1. Field of the Invention
The present invention relates to an image pickup apparatus capable of inputting an image of substantially high image quality by finely varying the optical angle of a parallel-plane plate glass or a reflecting mirror which is provided in the optical path of an image pickup system.
2. Description of Related Art
In recent years, image input apparatus such as video cameras and scanners have made remarkable advances, and far higher image quality and far higher resolution have been strongly demanded. However, to increase the number of pixels per image pickup element involves a number of problems, such as performance problems such as a lowering in sensitivity or S/N, an increase in cost due to a decrease in production yield, and the necessity for an expensive quartz-crystal low-pass filter or the like for preventing a false signal or the like.
What is called xe2x80x9cpixel shiftingxe2x80x9d is known as a method of increasing the image quality and the resolution of an image pickup apparatus without increasing the number of pixels per image pickup element. The pixel shifting is a method of finely vibrating an image pickup element itself or sequentially obtaining optical-video information by conducting, to photosensitive portions on the image pickup element, optical-image information which would have reached non-photosensitive portions between adjacent photosensitive portions, while varying the reflection angle of a reflecting mirror disposed in an optical path in an optical relay space between a lens group and the image pickup element or while varying the incident angle of light on an optical transmission glass having the shape of a parallel-plane plate or varying the thickness of the optical transmission glass by using the refraction of light by the optical transmission glass which is disposed in such optical path. According to such pixel shifting, it is possible to obtain an image having a high resolution which is substantially equivalent to a resolution obtainable when the number of pixels of an image pickup element is increased.
Since this method makes it possible to pick up an image of high image quality without increasing the number of pixels of the image pickup element itself, the pixel shifting is a method which is extremely effective in increasing the resolution of the image input apparatus.
Specific examples of pixel shifting using the above-described principles have been disclosed. For example, Japanese Laid-Open Patent Application No. Sho 59-15378 discloses the art of rotating a parallel-plane plate about an axis parallel to a pixel array, Japanese Laid-Open Patent Application No. Hei 1-121816 discloses the art of inclining a parallel-plane plate surface and rotating it about an optical axis, and Japanese Laid-Open Utility Model Application No. Hei 6-8937 discloses the art of driving a cam mechanism by means of a motor and varying the inclination of a parallel-plane plate surface in the directions of X and Y axes.
However, in any of the above-described conventional mechanism examples which use a parallel-plane plate optical-transmission glass, a motor is used as a drive source which varies the optical position of the parallel-plane plate optical-transmission glass and a complicated expensive mechanism such as a position control mechanism using a cam, with the result that it is difficult to ensure the positioning accuracy of the parallel-plane plate optical-transmission glass and it is also difficult to increase the driving speed thereof.
If two horizontal and vertical systems each including a motor, a cam and a mechanism for transmitting the drive force of the motor are incorporated in an image pickup apparatus, a number of problem will occur; for example, the entire pixel shifting mechanism necessarily become larger in size and difficult to dispose in the space between the lens group and the image pickup element.
The present invention has been made to solve the above-described problems, and its first object is to provide a pixel shifting method, an optical (pixel shifting) apparatus and an image pickup apparatus all of which are capable of realizing high-speed driving by using a simple arrangement.
A second object of the present invention is to provide a pixel shifting method and an optical (pixel shifting) apparatus both of which are capable of realizing pixel shifting of multiple steps and control of the amount of pixel shifting by using an extremely simple arrangement without the need for a complicated arrangement.
A third object of the present invention is to provide an optical apparatus which enables pixel shifting which is easy to control and can be driven at extremely high speed without the need for a complicated mechanism.
To achieve the above objects, in accordance with one aspect of the present invention, there is provided an optical apparatus which comprises an optical element for shifting a position of an incident light beam on an image forming plane, a plurality of restricting portions for controlling an inclination position of the optical element with respect to an optical axis by respectively restricting end portions of the optical element, and driving means for driving the optical element to the restricting portions.
To achieve the above objects, in accordance with another aspect of the present invention, there is provided an optical apparatus which has position restricting surfaces formed before and behind each end portion of an optical element in the direction of the optical axis and determines the inclination angle of the optical element relative to the optical axis by restricting the position of each end portion of the optical element in the direction of the optical axis by means of the position restricting surfaces, the optical element being capable of being controlled to move among a plurality of inclination angles, by modifying a combination of the position restricting surfaces which the end portions of the optical element selectively come into abutment with.
In accordance with another aspect of the present invention, there is provided an optical apparatus in which a drive source for driving a parallel-plane plate disposed in an image pickup optical system includes a plurality of electromagnets and is arranged to vary the inclination position of the optical element by performing on-off control of each of the electromagnets to select the position restricting surfaces which the optical element comes into abutment with.
In accordance with another aspect of the present invention, there is provided an optical apparatus which is provided with a plurality of optical elements and a plurality of restricting portions and is arranged to determine an entire amount of image shifting by combining the amounts of image shifting of a light beam according to the respective inclination positions of the plurality of optical elements.
A fourth object of the present invention is to integrate a pixel shifting mechanism with an optical apparatus as one unit and improve the applicability of the pixel shifting mechanism to various lens units and cameras as well as the versatility of the pixel shifting mechanism.
A fifth object of the present invention is to provide a lens unit in which a pixel shifting mechanism is incorporated.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.